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PO-710-03 TEMPORAL AND SPATIAL EVOLUTION OF REVERSIBLE AND IRREVERSIBLE VENTRICULAR LESION BOUNDARIES PRODUCED BY PULSED ELECTRIC FIELD ABLATION

      Background

      During pulsed electric field (PEF) ablation, electric pulses induce reversible (R) or irreversible (IR) injury on cardiac myocytes. Using triphenyl tetrazolium chloride (TTC) staining, we have reported that acute PEF ablation lesions show a dark central zone (DCZ, contraction band necrosis and hemorrhage) surrounded by pale boundary (PB, no mitochondrial activity, consistent with IR zone) and a hyperstained rim (HR, indicating enhanced mitochondrial activity) beyond the PB, indicating R zone.

      Objective

      To assess histologically the spatial extent and temporal evolution of PEF ablation lesions in a swine model.

      Methods

      A 7Fr catheter with a 3.5 mm ablation electrode (TactiCath, Abbott) was connected to a PEF generator (CENTAURI, Galaxy Medical) and positioned in RV and LV under EnSite guidance in 4 closed chest pigs. Biphasic PEF current (19 A, total duration 1.4 ms) was delivered between the ablation electrode and a skin patch at 50 ventricular sites at different target timepoints of <30 min, 1hr, 2hrs, 4hrs and 14 days after ablation. TTC was infused prior to animal sacrifice.

      Results

      Fig. The HR was initially greatest (<30 min) and gradually decreased over time while PB increased up to 4hr after ablation. The DCZ became evident only after 1hr and increased up to 4hr after ablation. At 14 days, ablation lesions show slightly smaller PB with no or minimal DCZ and HR. Histology showed fibrosis within the PB at 14 days, consistent with IR zone.

      Conclusion

      TTC staining showed dynamic temporal and spatial evolution of the DCZ, PB and HR. The large initial HR zone indicates IR lesions are surrounded by relatively large R zone even 4hrs after ablation, suggesting the mechanism of transient conduction block during PEF ablation.
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